Photographic hydrophilic colloids and method of coating

ABSTRACT

A composition is disclosed which comprises a solution of a hydrophilic colloid and a viscosity increasing concentration of a polysaccharide comprising a linear polymer in which either (1) at least one-third of the monosaccharide units are linked 1-2 and the remaining monosaccharide units are linked 1-4, or (2) substantially all monosaccharide units are linked 1-4 and at least 50 percent of the hydroxyl groups are acetylated or alkali metal sulfated.

United States Patent 1 Brust et al.

1 Oct. 23, 1973 PHOTOGRAPHIC HYDROPHILIC COLLOIDS AND METHOD OF COATING Inventors: David Philip Brust; Grace Eileen Kane, both of Rochester, N.Y.

Assignee:' Eastman Kodak Company,

Rochester, N.Y.

Filed: Feb. 22, 1972 Appl. No.: 228,379

U.S. Cl 96/94, 96/1 14.3, 106/125 Int. Cl. G03c 1/02 Field of Search 96/94, 114.3

References Cited UNITED STATES PATENTS 7/1968 Barnes et al. 96/61 Primary Examiner-Norman G. Torchin Assistant Examiner-Alfonso T. Suro Pico Attorney-Robert W. Hampton et al.

[57] ABSTRACT A composition is disclosed which comprises a solution of a hydrophilic colloid and a viscosity increasing concentration of a polysaccharide comprising a linear polymer in which either (1) at least one-third of the monosaccharide units are linked 1-2 and the remaining monosaccharide units are linked l-4, or (2) substantially all monosaccharide units are linked 1-4 and at least 50 percent of the hydroxyl groups are acetylated or alkali metal sulfated.

4 Claims, No Drawings BACKGROUND oF THE INVENTION 1. Field of the Invention This invention relates to the use of viscosityincreasing materials or thickening agents in dilute compositions of hydrophilic colloids. In one specific aspect, this invention relates to the incorporation of linear polysaccaride polymers as thickening agents in dilute gelatin photographic emulsions to improve the coatability thereof.

2. Description of the Prior Art It is well-known that most photographic emulsions contain gelatin. It is also known that low gelatin concentrations permit coating of thin layers. Various thickening agents which have been used to facilitate the coating of dilute photographicemulsions include: carboxy-methylated carbohydrates, cellulose derivatives,-

carrageenans, alginic acid, various acrylic acid polyniers, water-soluble sulfonate polymers, pectic polysaccharides (Belgian Pat. No. 61 1,623), dextran (US. Pat. No. 3,063,838) and certain other polysaccharides (US. Pat. Nos. 2,942,974; 3,085,009 and 3,338,716 and Belgian Pat. No. 665,862)."None of these materials has been entirely satisfactory and they exhibit problems producing haze, coagulation, brittleness, etc.

Materials used previously as viscosity increasers for.

hydrophilic colloids have exhibited still other problems such as salt-sensitivity, wherein reduced viscosity improvements are obtained in the presence of watersoluble salts. Increases in viscosity have also been restrained by particular pI-I environments and the presence of polyvalent cations like cadmium. The deleterious effect of polyvalent cations is most characteristic with thickening agents having carboxyl groups However, improved silver halide emulsions'having low gelatin content and increased viscosity are desired in order to coat improved thin layers in photographic elements without substantially affectingthe other physical and photographic properties of the element. I

Accordingly, an object of this invention is to increase the viscosity of hydrophilic colloid'solutions, including gelatin solutions.v a v Other objects of this invention are .to coat dilute aqueous hydrophilic colloid solutions of increased viscosity and to produce photographic elements using such colloid solutions.-

Still other objects and-advantages of the present invention will become apparent from a reading of the specification and claims.

SUMMARY OF THE INVENTION I-lydrophilic colloid solutions, e. g. gelatin solutions, exhibit an increase in viscosity in the presence of an effective amount, i.e., a viscosity increasing concentration, of a polysaccharide that is a linear polymer in which either (1) at least one-third of the monosaccharide units are linked 1-2 and the remaining monosacof about 0.001 to about 0.5 percent by weight, based on the colloid, are typical. Polysaccharides of the present types are especially useful in aqueous colloid solutions wherein the colloid is present in an amount of from about 0.1 to about 6 weight percent, based on the total solution weight. Colloid solutions are useful as photographic solutions and can comprise photographic silver halide emulsions. Such solutions and emulsions can be used to advantage when coated to form photographic layers, for example, as an integral photographic layer in a photographic element.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In one embodiment, the present invention relates to solutions including a hydrophilic colloid and a viscosity increasing concentration of a polysaccharide including linear polymers in which either (1) at least one-third of the monosaccharide units are linked l-2 and the remaining monosaccharide units are linked l-4, or (2) substantially all monosaccharide units are linked 1-4 and, as regards these'polysaccharides with all monosaccharide units linked l-4, at least about 50 percent of the hydroxyl groups are acetylated or alkali metal sulfated. Polysaccharides of this type are especially useful for increasing the viscosity of aqueous colloid solutions wherein the colloid ranges from about 0.1 to about 6 percent by weight, based on total solution weight. Most generally, viscosity increasing concentrations range from about 0.001 to about 0.5 weight percent, preferably from 0.001 to about 0.2 weight percent, based on the colloid, but more extensive variations are possible where desired. A wideyrange of hydrophilic colloid solutions can be increased in viscosity with polysaccharides of the present types, and they are especially useful for thickening photographic hydrophilic colloid solutions, gelatin for example.

. In a preferred aspect, the present invention includes compositions comprising a solution of a hydrophilic colloid, e.g. gelatin, preferably in the range of from about 0.1 to about 6 percent by weight of the composition and a viscosity increasing concentration of a bacterial polysaccharide that is either a B-l459 or a B-l973 polysaccharide. Viscosity increasing concentrations are widely variable, but concentrations (as described elsewhere herein) are used for conventional situations.

Polysaccharides such as the 8-1459 and 8-1973 polymers described herein are specific polymers that are biosynthesized by particular bacterial strains. Polysaccharides of this type are named asa function of the bacteria that effects the biosynthesis. This is a method well recognized in the literature and provides a complete description for stereospecific bacterial polysaccharides.

References identifying polysaccharides B-l459 and- /or 8-1973 include the following:

Orentas, D. G., et al., Canadian J. Microbiology, 9, 427 (1963).

Sloneker, J. H., et al., Canadian J. Chemistry, 46, 3,353 (1968).

Wallen, L. L., et al., Appl. Microbiology, 13, 272 (1965).

Slodki, M. E., Biochim. Biophys. Acta 69, as well as US. Pat. Nos. 3,383,307; 3,516,983; 3,391,061 and 3,000,790.

Further, the theoretical structure of polysaccharides B-l459 and 8-1 973 has been characterized by the following structural formulas M B-D-mannose G B-D-glucose GA= B-D-glucuronic acid CHiOH CHrOH COzK 4-OAcetyl groups where X is S0 M and M is an alkali metal.

Using polysaccharides of the types described herein, another embodiment of the present invention relates to dilute silver halide photographic emulsions of improved coatability, particularly to gelatino silver halide emulsions containing less than about 6 weight percent gelatin, that are thickened by the addition of a viscosity increasing concentration of a polysaccharide as described herein. Still another embodiment of this invention is a coating process for preparing layers from improved hydrophilic colloid compositions particularly aqueous gelatin compositions including silver halide emulsions and especially those having less than 6 weight percent gelatin.

Using the dilute hydrophilic colloid compositions and processes of this invention permits the coating of thinner layers in photographic elements by eliminating a portion of the colloid vehicle without decreasing viscosity. This results in photographic elements of increased image sharpness and more rapid processing characteristics without loss of coating uniformity. Also, a greater numbers of layers can be incorporated into multilayer packs. Special hardeners are not required since conventional hydrophilic colloid hardeners such as gelatin hardeners can be used to harden the emulsions or other compositions.

The colloidal materials whose properties are improved by mixing with a polysaccharide of the present types are those whose dispersions or solutions are recognized as desirable vehicles in photographic emulsions and elements, especially those pbotographic elements having multiple layers. Included are gelatins, glues, pigmented gelatins, gelatin derivatives and other colloidal materials like poly (acrylamide), poly(vinyl alcohol), poly(vinyl pyrrolidone), polysaccharides such as dextran, gum arabic and the like, either alone or in combination with gelatin being preferred.

The described colloid solutions or photographic emulsions can also contain dispersed vinyl polymers, particularly those which increase the dimensional stability of photographic materials. Suitable synthetic polymers include those described, for example, in U. S. Pat. Nos. 3,142,568; 3,193,386; 3,062,674; 3,220,844; 3,287,289 and 3,411,911; and include, for example, the water-insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkylacrylates or methacrylates and the like.

' Polysaccharides of the present types can be added to" 7 onto the film or paper support.

As mentioned elsewhere, the polysaccharide need not necessarily be added to a silver halide emulsion or layer, but can be added to photographic solutions or emulsions used as subcoats or overcoats for the photographic element.

Dilute aqueous compositions thickened as described can be coated on a wide variety of supports in singleor multilayer photographic. elements, for example, as disclosed in Russell, U.S.'Pat. No. 2,761,791, issued Sept. 4, 1966. The compositions of this invention can also be coated by dip-coating methods or. methods where high viscosity is quite advantageous such as in extrusion coating, curtain coating and doctor knife coating. Examples of suitable supports include cellulose nitrate filrn, cellulose ester film, polyvinyl acetal film, polystyrene film, poly(ethylene terephthalate) film and related films or resinous materials as well as glass, paper, metal and the like. Supports such as paper which are coated with a-olefin polymers, particularly polymers of a-olefins containing two or more carbon atoms, e.g., polyethylene, polypropylene and ethylene butene copolymers, can also be employed.

Photographic elements can be produced comprising a support and integral layers in which at least one layer comprises a silver halide emulsion, for example, the improved viscosity compositions can be used to coat interlayers, silver halide emulsion layerspdye mordant layers, receiving layers and the like. The compositions of the invention improved as described can be coated in thin, uniform layers thereby permitting a combination of more of said layers into a thin photographic element.

Silver halide photographicemulsions and elements of the invention can be used. in various kinds of photographic systems, e.g., monochromatic, orthochromatic, panchromatic, infrared,'X-ray and other non-optically sensitized systems. Silver halide photographic emulsions and elements improved as described can be used in color photography, e.g., emulsions containing colorforming couplers or emulsions to be developed by solutions incorporating couplers or other color-generating materials.

The integral layers of a photographic element can be chemically sensitized, e.g., with noble metal sensitizers alone or in combination with sulfur or selenium sensitizers. They can contain spectral sensitizers such as, for example, the cyanines, merocyanines, complex (trinuclear) cyanines, complex merocyanines, styryls and hemicyanines. Sensitizing dyes useful in such integral layers are described, for example, in US. Pat. Nos. 2,526,632 and 2,503,776.

The integral layers of a photographic element can also contain development modifiers such as polymeric EXAMPLE 1 g A 1 percent aqueous solution of a commercially available Xanthomonas polysaccharide marketed under the trade name Kelzan by the Kelco Company and produced by the aerobic fermentation of glucose by the bacterium Xanthomonas Campestris NRRL 8-1459 was filtered through paper in a pressure filter and the concentration determined gravimetrically by evaporation.

Nine solutions (Nos. 1-9) of gelatin from 1 to 7 percent bone gelatin were made, each containing 0.1 percent polysaccharide. The Brookfield viscosities of these solutions, as well as the corresponding gelatin solutions, were determined in centipoises (cps.) at 40 C. The results in Table I demonstrate the large viscosity increase produced by a small amount of the Xanthomonas Campestris polysaccharide (B-l459) in aqueous gelatin.

A solution of 0.1 percent B-1459 polysaccharide and 5 percent bone gelatin was prepared at 40 C. The Brookfield viscosity was determined as the pH was raised by the addition of dilute sodium hydroxide. The results are summarized in Table II and they indicate that over the pH range considered the viscosity was not very sensitive to pH change.

TABLE II Effect of pH Change on Viscosity of Gelatin B-1459" Polysaccharide Solution pH Viscosity 40 p EXAMPLE 3 A solution of 0.1 percent by weight based on the gelatin of 13-1459 polysaccharide and 5 percent by weight bone gelatin was prepared at 40 C and the pH adjusted to 6.1. Addition of sodium chloride in increments up to 0.2 molar had little effect on the Brookfield viscosity.

TABLE 111 Effect of Concentration of Sodium Chloride on the Viscosity of Gelatin-B4459 Polysaccharide Solution NaCl Brookfield Molarity Viscosity 40 W) 7 EXAMPLE 4 Coatings of a bone gelatin solution containing increasing amounts of B-l459 polysaccharide were made on poly(ethylene terephthalate) support. The results summarized in Table IV indicate that the polysaccharide at useful levels has little or no effect on the light transmittance of the gelatin coatings.

TABLE IV Spread Gelatin B-1459 Gelatin 13-1459 Light Transmission at 520nm Wt.% Wt. mg/ft mg/ft Specular Total 0 90.0 91.2 0 1000 0 90.5 91.0 5 0.017 1000 3.3 90.5 91.0 5 0.025 1000 5.0 90.5 91.0 5 0.05 1000 90.5 91.0 5 0.10 1000 20 90.0 91.0 5 0.20 1000 40 89.8 91.0

EXAMPLE 5 One mole of a silver bromoiodide emulsion containing 47 g. of gelatin was adjusted to a total weight of 835 g. with distilled water. Increasing levels of B-l459 polysaccharide, varying from 0.01 percent to 0.10 percent by weight, based on the gelatin, were added to three separate aliquot portions of the gelatino emulsion. A fourth portion with no polysaccharide served as the control. The Brookfield viscosity was measured at 40 C at a pH of 6.5. The results summarized below in Table V, demonstrate the efficacy of small amounts of B-l459 polysaccharide for increasing the viscosity of a gelatino-silver halide emulsion.

TABLE V B-1459 Brookfield Wt. Viscosity 40 EXAMPLE 6 dried. The following results, summarized in Table Vl,

indicate that the B-l459 polysaccharide does not interfere with the sensitometry of photographic emulsions.

TABLE VI Sensitometric effect 01 13-1459 polysaccharide on a gelatino-silver halide emulsion 1 wk. inc. 120, Hold Fresh 50% R.H.

time 13-1459 at 40 C. g./mole Rel. Gross Rel. Gross Melt (hr.) Ag speed 1 log speed v for:

Al 4 0 100 1. 27 08 67 0. 92 .08 B1 0 0 120 1.30 .07 80 1.00 .06 A2 4 2 115 1.34 .08 80 .08 .08 B2 0 2 126 1. 35 .08 87 1.05 .06 A3... 4 4 126 1.41 .08 87 1.05 .08 B3 0 4 120 1. 36 08 87 1. 05 08 EXAMPLE 7 The viscosities of various aqueous solutions were measured on an Epprecht Rheomat at a temperature of 40 C. These data, which appear in the following table, were computer analyzed resulting in the viscosity as a function of shear rate.

The polysaccharide-gelatin solutions decrease exponentially in viscosity as the shear rate is increased. The gelatin solutions do not vary significantly in viscosity with increasing shear rates and is considered to be Newtonian behavior.

Kelzan D is a form of polysaccharide B-l459 which has been modified for use in systems with other gum or cellulose materials (Kelco Co., Technical Bulletin 15).

EXAMPLE 8 Kelco SCS is a water soluble sodium cellulose sulfate gum having a high degree of substitution (approximately 2.5 sulfate groups per anhydroglucose unit).

Kelco SCS was added as an aqueous solution (0.1 percent by weight) to an aqueous solution of gelatin (5 percent by weight) and the viscosities (poise) was measured at various pl-ls and at two shear rates (27 sec and 48 sec") at 40 C.

Shear Rate pH 27 sec 48 sec 4.93 0.873 poise 0.779 poise 5.85 0.786 poise 0.676 poise 7.33 0.385 poise 0.349 poise 9.16 0.281 poise 0.256 poise control (no Kelco SCS) 0.053 poise The salt sensitivity of Kelco SCS is determined by adding increasing amounts of an aqueous solution of potassium nitrate to a gelatin solution (5 percent by weight) and measuring the viscosity (poise) at a constant shear rate (sec).

TABLE VIII 27 sec 48 sec" 1. 5% gelatin 0.052 poise 2. 1 1% Kelco SCS 0.685 poise 0.605 poise 3. 2 0.025M KNO; 0.293 poise 0.270 poise 4. 2 0.05 KNO, 0.180 poise 0.166 poise 5. 2 0.10M KNO 0.010 poise 0.096 poise The above date show that Kelco SCS exhibits salt sensitivity at high concentrations of potassium nitrate but shows only moderate pH sensitivity.

This invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

What is claimed is:

1. In a method for increasing the viscosity of an aqueous composition of a photographic silver halide emulsion containing a hydrophilic colloid, the improvement which comprises incorporating therein a viscosity increasing concentration of a polysaccharide comprising a linear polymer in which either (1) at least one-third of the monosaccharide units are linked 1-4, or (2) substantially all monosaccharide units are linked 1-4 and at least 50 percent of the hydroxyl groups are acetylated or alkali metal sulfated.

3. A photographic element comprising a support having thereon at least one layer comprising a silver halide emulsion and at least one layer, which can be the same as or different from said emulsion layer, comprising a hydrophilic colloid having therein, in a concentration of from about 0.001 to about 0.2 weight percent based on the colloid, of a bacterial polysaccharide that is either a B-l459 polysaccharide, a B-l973 polysaccharide or a polysaccharide of the structure where X is -SO M and M is an alkali metal.

4. A silver halide emulsion comprising a photographic hydrophilic colloid solution comprising about 0.1 to about 6 weight percent colloid and a bacterial polysaccharide that is either a B-l459 polysaccharide, a B-l973 polysaccharide or a polysaccharide of the structure wherein X is -SO M and M is an alkali metal, said polysaccharide being in a concentration of from about 0.001 to about 0.2 percent by weight based on the colloid.

Disclaimer 3,767,410.Dwid Philip Ernst and Grace E ileen Kane, Rochester, N.Y. PHO- TOGRAPHIG HYDROPHILIC COLLOIDS AND METHOD OF COATING. Patent dated Oct. 23, 197 3. Disclaimer filed July 11, 1974, by the assignee, Eastmn Kodak Company. Hereby enters this disclaimer to claims 1, 2, 3 and 4 of said patent.

[Ofiioial Gazette J1me 10, 1.975.] 

2. A photographic element comprising a support and integral layers, at least one layer comprising a photographic silver halide emulsion, wherein said integral layers contain a composition of matter comprising a solution of a hydrophilic colloid and a viscosity increasing concentration of a polysaccharide comPrising a linear polymer in which either (1) at least one-third of the monosaccharide units are linked 1-2 and the remaining monosaccharide units are linked 1-4, or (2) substantially all monosaccharide units are linked 1-4, and at least 50 percent of the hydroxyl groups are acetylated or alkali metal sulfated.
 3. A photographic element comprising a support having thereon at least one layer comprising a silver halide emulsion and at least one layer, which can be the same as or different from said emulsion layer, comprising a hydrophilic colloid having therein, in a concentration of from about 0.001 to about 0.2 weight percent based on the colloid, of a bacterial polysaccharide that is either a B-1459 polysaccharide, a B-1973 polysaccharide or a polysaccharide of the structure
 4. A silver halide emulsion comprising a photographic hydrophilic colloid solution comprising about 0.1 to about 6 weight percent colloid and a bacterial polysaccharide that is either a B-1459 polysaccharide, a B-1973 polysaccharide or a polysaccharide of the structure 